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Knowledge base
Guides & explainers
Knowledge base
79 articles across 13 categories — free to read, no account needed.
Finance & Money
(21)
Health & Fitness
(5)
Math & Numbers
(2)
Date & Time
(6)
Units & Conversion
(3)
Text & Writing
(2)
Developer Tools
(13)
Design & Color
(3)
SEO & Marketing
(1)
Random & Generators
(2)
Everyday & Lifestyle
(9)
AI & LLM Tools
(5)
Crypto Tools
(7)
Finance & Money
21 articles
What is EMI?
Learn what EMI is, how the amortization formula works, and how to calculate your monthly loan payment. Includes examples for mortgages and personal loans.
Published Apr 17, 2026
How to Calculate a Loan EMI
Learn how to calculate Equated Monthly Installments (EMI) for a loan. Understand the EMI formula, how interest rate and tenure affect payments, and tips to reduce total interest paid.
Published Apr 17, 2026
How to Calculate Mortgage Payments
Learn how monthly mortgage payments are calculated, what factors affect your repayment, the difference between fixed and variable rates, and how to reduce total interest paid.
Published Apr 17, 2026
What Is Compound Interest and How Does It Work?
Understand compound interest, how it differs from simple interest, how compounding frequency affects growth, and how to use the compound interest formula to grow savings.
Published Apr 17, 2026
How to Calculate GST and VAT
Learn how to calculate GST (Goods and Services Tax) and VAT (Value Added Tax), add tax to a price, extract tax from a gross amount, and understand tax-inclusive vs exclusive pricing.
Published Apr 17, 2026
How to Calculate Your Retirement Savings Goal
Learn how to estimate the savings needed for retirement using the 4% rule, how to factor in inflation, Social Security or pension income, and how to close a savings gap.
Published Apr 17, 2026
How to Set and Reach a Savings Goal
Learn how to calculate how long it will take to reach a savings target, how much to save each month, and strategies to accelerate progress toward any financial goal.
Published Apr 17, 2026
Simple vs Compound Interest -- When Each Applies
Simple vs Compound Interest -- When Each Applies -- Simple interest grows only on the principal. Compound interest grows on the principal plus interest already...
Published May 1, 2026
What Is Loan Amortization?
What Is Loan Amortization? -- Amortization is the schedule that pays down a loan over time. Each payment covers interest on the remaining balance plus a slice...
Published May 1, 2026
Fixed vs Adjustable Mortgage Rates -- Trade-offs
Fixed vs Adjustable Mortgage Rates -- Trade-offs -- A fixed rate mortgage locks the interest rate for the life of the loan (or a long fixed window). An ARM (ad...
Published May 1, 2026
Exchange Rate Spreads -- Mid-Market vs What You Pay
Exchange Rate Spreads -- Mid-Market vs What You Pay -- Mid market rates (often published by central banks) sit between the bid and ask in wholesale FX. Retail...
Published May 1, 2026
Discount, Markup, and Margin -- Related but Different
Discount, Markup, and Margin -- Related but Different -- Discount reduces a list price. Markup adds profit on top of cost. Margin expresses profit as a percent...
Published May 1, 2026
Gross vs Net Price After Tax
Gross vs Net Price After Tax -- Net usually means before tax; gross includes tax -- or the opposite in payroll! In retail, clarify whether a shelf tag is VAT i...
Published May 1, 2026
APR vs APY -- Nominal Rate vs Yield
APR vs APY -- Nominal Rate vs Yield -- APR often quotes a simple annual loan rate without fully compounding fees. APY (annual percentage yield) reflects compou...
Published May 1, 2026
Gross Pay vs Net Pay -- What Take-Home Estimates Miss
Gross Pay vs Net Pay -- Gross is headline compensation. Net is after taxes and deductions -- but not identical to take-home pay. Covers tax withholding and deductions.
Published May 1, 2026
GST Inclusive vs Exclusive Pricing
GST Inclusive vs Exclusive Pricing -- Some jurisdictions display tax inclusive shelf prices; B2B invoices may show exclusive lines plus VAT/GST lines.
Published May 1, 2026
What Is Gross Margin?
Understand gross margin -- the percentage of revenue remaining after subtracting COGS. Covers the formula, margin vs markup, typical margins by industry, and why it matters.
Published May 6, 2026
What Is the Break-Even Point?
Learn what the break-even point is, how to calculate it from fixed costs and contribution margin, and how to use break-even analysis for pricing and business planning.
Published May 6, 2026
How to Set Your Freelance Rate
A step-by-step guide to calculating your freelance floor rate from income target, expenses, and billable hours -- plus how to research market rates and avoid common pricing mistakes.
Published May 6, 2026
What Is the FIRE Number?
Everything you need to know about the FIRE number -- the 4% rule, how to calculate your target, FIRE variants (lean, fat, barista, coast), and what to include in annual expenses.
Published May 6, 2026
How to Invoice as a Freelancer
What every freelance invoice needs, how to calculate totals with tax (VAT/GST), when to send invoices, payment terms, and tools to generate professional invoice PDFs.
Published May 6, 2026
Health & Fitness
5 articles
What Is BMI?
Learn what Body Mass Index (BMI) is, how it is calculated, what BMI ranges mean for health, and when BMI may not be the best measure to use.
Published Apr 17, 2026
What Is BMR (Basal Metabolic Rate)?
Understand Basal Metabolic Rate (BMR), how it is calculated with Mifflin-St Jeor and Harris-Benedict equations, and how to use it to manage your weight.
Published Apr 17, 2026
How to Count Calories for Weight Loss or Gain
A practical guide to counting calories -- calculating your TDEE, setting a calorie target, tracking macros, and avoiding common mistakes that stall progress.
Published Apr 17, 2026
When BMI Is Misleading -- Accuracy Limits
When BMI Is Misleading -- Accuracy Limits -- BMI is cheap population screening: weight divided by height squared. It ignores body composition, fat distribution...
Published May 1, 2026
TDEE vs BMR -- What’s the Difference?
TDEE vs BMR -- What’s the Difference? -- BMR (Basal Metabolic Rate) is resting energy needs -- organs, temperature, repair. TDEE multiplies BMR by an activity f...
Published May 1, 2026
Math & Numbers
2 articles
What Is a Percentage?
Learn what percentages are, how to calculate them, and where they appear in everyday life -- from discounts and interest rates to test scores and statistics.
Published Apr 17, 2026
What Is Binary? Number Systems Explained
Learn how binary, octal, and hexadecimal number systems work, how to convert between them and decimal, and why computers use binary internally for all data.
Published Apr 17, 2026
Date & Time
6 articles
How to Calculate Age from a Date of Birth
Learn how to accurately calculate age in years, months, and days from a date of birth, how leap years affect the calculation, and common pitfalls in age arithmetic.
Published Apr 17, 2026
How to Calculate the Difference Between Two Dates
Learn how to calculate the exact number of days, weeks, months, and years between two dates, handle leap years correctly, and work with time zones in date arithmetic.
Published Apr 17, 2026
What Is a Unix Timestamp?
What Is a Unix Timestamp? -- A Unix timestamp counts seconds (traditionally) since 1970 01 01 00:00:00 UTC, not counting leap seconds in most APIs.
Published May 1, 2026
UTC vs Local Midnight -- Why Today Moves
UTC vs Local Midnight: UTC is a stable civil time baseline. Local midnight depends on your offset and daylight saving rules. That is why...
Published May 1, 2026
Daylight Saving Time Edge Cases
Daylight Saving Time Edge Cases -- When clocks spring forward, one local hour does not exist. When they fall back, the same local time happens twice. Calendar...
Published May 1, 2026
Leap Years and Age Calculations
Leap Years and Age Calculations -- Leap years exist to keep calendar years aligned with Earth’s orbit. For age in years, most software counts full calendar an...
Published May 1, 2026
Units & Conversion
3 articles
How to Convert Units
A practical guide to converting between metric and imperial units. Includes the most common conversions and the formulas behind them.
Published Apr 17, 2026
How to Convert Temperature Units
Learn the formulas to convert between Celsius, Fahrenheit, and Kelvin temperature scales, with worked examples and a quick-reference conversion table for common values.
Published Apr 17, 2026
Binary vs Decimal File Sizes -- MB, MiB, and Marketing TB
Binary vs decimal file sizes (MB vs MiB): why marketed TB exceeds Windows GB labels. Learn label math, OS overhead, and decimal SI vs binary IEC units.
Published May 1, 2026
Text & Writing
2 articles
What Is Markdown? A Plain-Text Formatting Guide
Learn what Markdown is, how its basic syntax works for headings, lists, links, and code, and where Markdown is used -- from GitHub READMEs to documentation and blogs.
Published Apr 17, 2026
What Is Lorem Ipsum? The History of Placeholder Text
Learn what Lorem Ipsum placeholder text is, where it comes from, why designers use it, and when to use real content instead of dummy text in your projects.
Published Apr 17, 2026
Developer Tools
13 articles
What is Base64 Encoding?
A clear explanation of Base64 encoding -- what it is, why it exists, and how to encode and decode text or binary data using it.
Published Apr 17, 2026
What Is a UUID?
Understand UUIDs -- universally unique identifiers. Learn the difference between UUID v4 and v7, how they are generated, and when to use them in software development.
Published Apr 17, 2026
What Is JSON?
Learn what JSON (JavaScript Object Notation) is, how to read and write it, common syntax errors, and best practices for using JSON in APIs and configuration files.
Published Apr 17, 2026
How to Use Base64 Encoding
Understand Base64 encoding -- what it is, how it works, when to use it, and common pitfalls. Includes examples for encoding images, JSON payloads, and credentials.
Published Apr 17, 2026
What Is a JWT (JSON Web Token)?
Learn what JSON Web Tokens are, how they are structured, how signature verification works, and best practices for using JWTs securely in web applications.
Published Apr 17, 2026
What Is Regex? A Beginner’s Guide to Regular Expressions
Learn what regular expressions (regex) are, how to read and write common patterns, and how to use regex for searching, validation, and text transformation.
Published Apr 17, 2026
What Is Cron? A Guide to Cron Expressions and Scheduling
Learn what cron is, how cron expressions work, how to read and write schedule patterns with the five-field syntax, and common cron examples for everyday scheduling tasks.
Published Apr 17, 2026
What Is URL Encoding and When Do You Need It?
Learn what URL encoding (percent-encoding) is, which characters must be encoded in URLs, the difference between encodeURI and encodeURIComponent, and how to decode URLs.
Published Apr 17, 2026
Choosing a Hash Algorithm -- SHA-256, SHA-1, MD5
Choosing a Hash Algorithm -- SHA-256, SHA-1, MD5 -- Cryptographic hashes map arbitrary data to a short fingerprint. Good hashes are fast to compute but hard to...
Published May 1, 2026
YAML or JSON -- Which Format Should You Use?
YAML or JSON -- Which Format Should You Use? -- JSON is strict, ubiquitous in APIs, and easy for machines to parse. YAML is human friendly for config files but...
Published May 1, 2026
Common JSON Syntax Mistakes (and Quick Fixes)
Common JSON Syntax Mistakes (and Quick Fixes) -- JSON looks simple until the comma bites you. Free reference with links to matching on-site calculators.
Published May 1, 2026
A Practical Regex Debugging Checklist
A Practical Regex Debugging Checklist -- Regex is dense -- debug systematically. Free reference with links to matching on-site calculators.
Published May 1, 2026
Unicode, UTF-8, and Why Encoding Matters for Developers
Unicode, UTF-8, and Why Encoding Matters for Developers -- Unicode assigns code points to characters. UTF 8 encodes those code points as bytes -- variable widt...
Published May 1, 2026
Design & Color
3 articles
What Is CSS Box Shadow? A Complete Guide
Learn how the CSS box-shadow property works, what each parameter controls, how to layer multiple shadows, and how to create common shadow effects for cards and buttons.
Published Apr 17, 2026
What Is a CSS Gradient? Linear, Radial, and Conic Gradients
Learn how CSS gradients work, the syntax for linear, radial, and conic gradients, how to add colour stops, angles, and transparency, and when to use each gradient type.
Published Apr 17, 2026
What Is Colour Theory? HEX, RGB, and HSL Explained
Learn the fundamentals of digital colour theory, how HEX, RGB, and HSL colour models work, how to convert between them, and how to build accessible colour palettes.
Published Apr 17, 2026
SEO & Marketing
1 article
UTM Parameters Explained for Marketers
UTM Parameters Explained for Marketers -- UTM tags are query parameters that analytics tools read to attribute traffic to campaigns -- without changing page co...
Published May 1, 2026
Random & Generators
2 articles
What Is a QR Code and How Does It Work?
Learn what QR codes are, how they encode data, what the different parts of a QR code do, and how to generate and scan them for URLs, contacts, and payments.
Published Apr 17, 2026
How to Generate and Manage Secure Passwords
Learn what makes a password strong, how password generators create random passwords, and how to manage dozens of strong passwords without memorising them all.
Published Apr 17, 2026
Everyday & Lifestyle
9 articles
How to Calculate a Tip and Split a Bill
Learn how to calculate a tip, choose an appropriate tip percentage, split a restaurant bill evenly or by individual items, and handle the maths when people order different amounts.
Published Apr 17, 2026
How to Calculate Fuel Cost for a Trip
Learn how to calculate fuel cost for any journey using consumption rate and fuel price, compare petrol vs diesel vs EV costs, and estimate annual vehicle running costs.
Published Apr 17, 2026
Sleep Cycles Explained: How to Wake Up Feeling Rested
Learn how sleep cycles and REM sleep work, why waking between cycles leaves you feeling refreshed, how long each cycle lasts, and how to calculate the best bedtime or wake time.
Published Apr 17, 2026
How to Track Work Hours and Calculate Pay
Learn how to track work hours accurately, calculate regular and overtime pay, convert between hourly and annual salary, and comply with working time rules.
Published Apr 17, 2026
How to Calculate a Weighted Grade Average
Understand how weighted grades work, walk through the formula step-by-step, and learn how to calculate your current standing mid-semester when not all grades are in.
Published Apr 29, 2026
What Score Do I Need on My Final Exam?
Learn the formula for calculating the exact score you need on your final exam to hit your target course grade, including what to do when the answer is over 100% or negative.
Published Apr 29, 2026
GPA to Percentage Conversion -- US 4.0 Scale
A clear reference table for converting between GPA and percentage grades on the US 4.0 with plus/minus scale, with common questions answered and a note on institutional variation.
Published Apr 29, 2026
SAT vs ACT Score Comparison -- Concordance Guide
Learn how to compare SAT and ACT scores using the official 2018 College Board concordance table, why conversions return ranges, and how colleges treat concordant scores.
Published Apr 29, 2026
How Many Hours Should You Study for an Exam?
A practical framework for estimating study hours based on your knowledge gap, subject difficulty, and days available, plus evidence-based tips for making those hours count.
Published Apr 29, 2026
AI & LLM Tools
5 articles
What Is an LLM Token? How AI Models Count Text
Learn what tokens are in large language models, why AI doesn’t count words or characters directly, and how tokenization affects your prompts, costs, and context limits.
Published May 3, 2026
How to Estimate AI API Costs Before You Build
A practical guide to estimating OpenAI, Anthropic, and Google AI API costs before committing to a model. Covers token math, request volume, and cost-per-feature budgeting.
Published May 3, 2026
GPT vs Claude vs Gemini -- API Pricing Compared
A side-by-side comparison of input and output token pricing for GPT-4o, Claude Sonnet, Gemini 1.5 Pro, and their cheaper variants. Includes cost estimates for common workloads.
Published May 3, 2026
Prompt Token Optimization -- How to Reduce AI API Bills
Seven practical techniques to reduce token usage without sacrificing output quality. Covers system prompt trimming, context management, model tiering, and caching strategies.
Published May 3, 2026
Context Windows Explained -- Tokens, Limits, and Long Prompts
What is a context window in AI models, how token limits work in practice, and what happens when your prompt exceeds the limit. Covers GPT-4o, Claude, and Gemini context sizes.
Published May 3, 2026
Crypto Tools
7 articles
What Is a Satoshi? Bitcoin Units Explained
Learn what a satoshi is, how Bitcoin’s unit hierarchy (BTC, mBTC, satoshi) works, and why the smallest unit matters for micropayments and fee calculations.
Published May 3, 2026
Gwei, Wei, and ETH -- Ethereum Units Explained
A clear breakdown of Ethereum’s unit system: Wei, Gwei, and ETH. Learn why Gwei is the standard unit for gas prices and how to convert between all three without losing precision.
Published May 3, 2026
How to Calculate Ethereum Gas Fees
Step-by-step guide to calculating Ethereum gas fees in ETH and USD. Covers gas units, gas price in Gwei, the EIP-1559 base fee model, and typical costs by transaction type.
Published May 3, 2026
How to Calculate Crypto Profit and ROI
Learn the formula for calculating crypto profit, loss, and return on investment. Includes examples for Bitcoin, Ethereum, and altcoins, plus a note on fees and taxes.
Published May 3, 2026
What Is Crypto Staking and How Do Rewards Work?
An introduction to proof-of-stake and crypto staking: how validators earn rewards, what APY means in staking, and the difference between custodial and non-custodial staking.
Published May 3, 2026
APY vs APR in Crypto -- What Validators and Protocols Report
Understand the difference between APR and APY in crypto staking and DeFi. Learn how compounding frequency affects your effective yield and why protocol dashboards often show different numbers.
Published May 3, 2026
Staking Risks -- Slashing, Lock-up Periods, and Market Risk
An honest look at the risks of crypto staking: slashing penalties, lock-up illiquidity, validator downtime, and the impact of price volatility on real returns.
Published May 3, 2026